Method of forming a blade root



Nov. 15, 1960 H. E. SPOONER 2, 60, 9

METHOD OF FORMING A BLADE ROOT Filed May 13, 1958 FIG.3

V W M I ll/1111 27 23 a 25 cw (1 JNVENTOR.

HOWARD E.SPOONER BY Kw? A M ATTOFE YS METHOD OF FORMING A BLADE ROOT Howard E. 'Spooner, Lincoln, R.I., assignor, by mesne assignments, to Engelhard Industries, Inc, Newark, NJ., a corporation of Delaware Filed May 13, 1958, Ser. No. 734,984

3 Claims. (Cl. 219-151) The present invention deals with a method of gathering a metal blade and more particularly with the method of forming a gathered root on the end of a metal blade.

Metal gathering of a metal blade as applied to this invention concerns the heat plasticizing of an end portion of a metal blade below melting temperatures and simultaneously forming the plasticized portion under pressure into an enlarged mass.

Metal blades of the type herein contemplated are used for stators, compressors and the like, e.g. blades for jet engine compressors, gas and steam turbines.

The invention relates to the gathering of a metal blade formed, for example, by rolling operations which pro vide a finished blade prior to gathering. However, the method of gathering an end of a blade according to the invention is also applicable to subsequently finished extruded or forged blades.

While it is possible to provide an enlarged mass at the end of an elongated substantially plasticized metal body by means of known upset forming techniques, it is extremely difficult to provide an enlarged desirably distributed gathered mass or root at the end of a thin metal blade especially of substantially thin airfoil contour. In the case of an airfoil type blade having a knife-like trailing edge, the trailing edge, due to its thin dimensions, does not plasticize as readily when resistance heated, as the thicker portions of the blade with the result that insufficient metal mass is deformed outwardly of the thin edge. Otherwise, under mass-forming pressure, strata are set up in the enlarged mass, especially in the mass in the vicinity of the thin edge, with the result that certain folds, stresses or strains are created in the gathered mass.

It is an object of the present invention to provide a method of gathering the end portion of a metal blade which permits desirable distribution of the gathered mass. It is another object of the present invention to provide a method for forming a shaped gathered metal root at the end of a metal blade. It is a further object of the present invention to provide an airfoil type metal blade by rolling operations and subsequently forming a root by metal gathering an end portion of the blade under heat and pressure. Other objects of the invention will become apparent from the description hereinafter following and the drawings forming a part hereof, in which:

Figure 1 illustrates a partly schematic and partly perspective view of an apparatus for gathering a metal blade according to the invention,

Figure 2 illustrates a fragmentary perspective view of a blade member,

Figure 3 illustrates a cross-sectional view of a pair of shaped rolls for forming a blade,

Figure 4 illustrates a perspective view of a blade produced in accordance with the invention, and

Figure 5 illustrates a. partly elevational and partly cross-sectional fragmentary view of a modification of the invention.

United States Patent 0 The invention deals with the method of forming a gathered root at the end of a metal blade by resistance heating the end of the blade to a plastic state, compressing the plasticized portion of the blade against an anvil, gathering the end of the blade under heat and pressure, and simultaneously selectively distributing the heating current to the gathering mass.

Preferably, the gathering mass is also simultaneously forged into a predetermined shape.

In the absence of selective distribution of the heating current, any portion of the blade end having cross-sectional dimensions less than that of another portion will carry less current, will have a lower state of plasticity and, consequently, will be less amenable to plastic deformation. In such case, insufficient gathered metal is deformed outwardly of the thinner portion of the blade end. Otherwise, in view of the lower plasticity at the thin edge of the blade, strata are formed in the gathered mass with the attendant creation of stresses or strains.

Regarding Figure l, the apparatus for effecting the method of the invention comprises a base member 1 with an anvil 2 secured or positioned on a surface thereof. A ram member 3, e.g. a pneumatic or hydraulically operated ram, is positioned in spaced relation to the anvil for movement toward the working surface of the anvil. A pair of electrodes 4 and 5 are positioned between the anvil 2 and ram 3 and are movable transversally of the anvil, e.g. transversally of the ram axis, with the contact faces thereof disposed oppositely of each other and adapted to clamp a workpiece, or blade, therebetween under opposing pressures, e.g. opposing hydraulic pressures. The contact faces 6 and 7 are essentially shaped to correspond with the surface contour of the blade :8 positioned therebetween for optimum electrical contact with the blade.

A transformer 9 having a primary winding 10 and a secondary winding 11 provides the heating current for performing the method of the invention. The secondary winding 11 of transformer 9 is connected to the base 1 by means of conductor 12 and to electrodes 4 and 5 by means of conductors 13, 14 and 15. The heating circuit is conventional and otherwise adequately illustrated by the drawing. The electrodes 4 and 5 are positioned in close proximity to the anvil 2 so as to provide a current path as short as possible in the blade 8 between anvil 2 and electrodes '4 and 5.

A cup 16 is positioned on the anvil 2 with the end portion 17 of blade 8 disposed in the cup cavity.

The base 1 is preferably composed of a metal or metal alloy having high electrical conductivity. The die 2 is composed of a hard metal resistant to high temperatures and deformation, e.g. metals such as tungsten, Zirconium, titanium, vanadium, etc., or alloys thereof. The cup 16 is composed of such hard metals or other metals as hereinafter more particularly described.

In operation, the heating current is applied to the electrodes and the base 1. The end of the blade 8 is resting on the inner surface of the cup 16 and the heating current follows a path through the blade portion between the electrodes and cup, through the cup and anvil, between the electrodes and base. The end of the blade 8 is under a nominal pressure of the ram 3 to provide a good surface contact engagement between blade and cup. It is understood that the heating of the blade is concentrated at the surface of contact between blade and cup due to the high resistance present at the contact surfaces. When the end of the blade contacting the cup 16 reaches a sufficiently plastic condition, the pressure on the end of the blade is increased by means of ram 3. With increased pressure, which is continued, the end of the blade 8 begins to gather as at 18 of Figure 1. Initially, the

plastic deformation occurs at the thicker cross-sectional portions of the blade because the heating current is substantially concentrated at such thicker portions. However, since the.end of the blade is confined within the cup .16, plastic deformation is directed toward the'thinnerportionsof the blade due to the confining function of the cup. "As the plastic mass moves toward'the thinner porv,tion of the blade, the heating current is automatically selectively distributed toward such thinner portion and effectively promotes a higher plastic condition of the blade at the thinner end and its amenability to deformation is increased with the attendant gathering thereof substantially without the formation of strata. Moreover, the confining efiect of the cup 16 effectively displaces gathered .metal in an adequate volume in the vicinity of the thin edges of the blade.

Instead of placing the cup 16 on the'surface of the 'die 2, the die maybe provided with a cavity 19 recessed thereintand the cup 16 seated in the cavity as illustrated 'by'Figure 5. However, the cavity 19' alone is adequate .in providing the currentxand mass distributing function.

As the gathered mass, e.g. mass 18, accumulates, the electrodes, which were'originally in close proximity to the anvil 2 or cup 16, are moved upwardly or in a direc .tion away from the accumulatingmass to enable the mass to build up its volume. Alternatively the base 1 and anvil 2 are moved downwardly as the mass 18 builds up.

As'hereinbefore stated, the blades are substantially thin 'and'may, for particularapplication, require a gathered root of substantial mass. An economical expedient for gprovidingsuch mass is the provision of added mass to the gathered root by making the cup of suitable metal,

e.g. a'metal of which the blade is composed, and Welding the cup to the gathered mass simultaneously with the gathering step. For example, the inside walls of the 'cup'are coated with a suitable layer of metal, e.g. nickel, and the cup is thereby effectively welded to the gathered mass under the applied pressure of the ram'3. The latter step is preferably carried out with the cup inserted in the die cavity 19 of Figure 5, whereby the gathering, "current distribution metal displacement, and a forging of the root mass against the cup 16 are accomplished simultaneously under the pressure of the ram 3.

Alternatively, the metal cup 16, or its equivalent, may be dispensed with if a particular root shape is not required. In such case, according to Figure 2, the selective distribution .of the current may be accomplished by Weld- .ing'a piece of metal 20 to the thin edge 21 of blade 8, "whereby under the'application of current and pressure -similarly to that hereinabove described, the current'is "selectively distributed to such thin edge of the blade 8,

.and the end of the blade is gathered against the working surface of anvil 2.

When the cup .16 is employed, or the anvil cavity 19 in absence of the cup 16, the finished blade is provided in the form illustrated by Figure 4 representing an'integral combination of blade 8 and root 22.

While blades, prior to gathering, may be preformed by extrusion or forging, such blades require costly finishing operations for providing satisfactory surface finish. The blades are, therefore, advantageously preformed by rolling methods which provide the finished preformed blade without requiring subsequent finishing apart from the root gathering method according to the invention. According to Figure 3, the blade 8 is producedvby rolling elongated stock 23 between .a pair of shaped rolls 24 and 25, and repeatedly passing the stock between the rolls until the desired shape and dimensions are attained. Roll 24 is provided with an annular convex surface 26 and roll 25 is provided with a complementary concave surface 27 with the stock 23 positioned between such complementary. surfaces. When the stock 23 is rolled to finished dimensions, the stock is cut into sections representing the preformed blades 8.

While the invention is particularly described in connection with apparatus illustrated, various modifications in the apparatus are contemplated within the'scope of the appended claims.

What is claimed is:

l. The method of forming a gathered root atthe end of a metal .airfoil blade of varying thickness, comprising adding metal at least to a thinner portion ofan end of the 'blade, resistance heating the end portion of the blade to which the metal has been added, compressing the heated portion of .the blade against .a die, and gathering the end of the blade under heat and pressure.

2. The method of forming a gathered root'at the'end of a metal airfoil blade of varying thickness, comprising adding metal at least to the thinner portion of an end'of the blade placing the end of the blade into a receptacle, resistance heating the end portion of the blade within the receptacle, compressing the heated portion of the blade into said receptacle, gathering the heated end of the blade within said receptacle, and simultaneously welding the gathered mass to the receptacle.

3. The method according to claim 1 wherein the added metal is welded at the end of the blade adjacent the thinnest edge thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,691,778 McDonald Nov. 13, 1928 2,638,663 Bartlett et al. May 19, 1953 2,726,307 Weaving et al. Dec. 6, 1955 2,836,706 Cavanagh May 27, 1958 2,890,325 Havlik June9, 1959 

